Insulated Case Does Double-Duty
Standard plastic coolers work fine, but if you don’t want to borrow the family’s food carriers, consider this Norchill insulated Cooler Bag. When not used to keep your ammo cool, the 7″ wide x 12″ high x 14″ long small Norchill Bag doubles as a gear carrier. Norchill bags feature dual-temp insulation and a waterproof inner liner. With side-zip compartments, Norchill Cooler Bags are more versatile than typical plastic coolers. These Norchill cooler bags are soft, collapsible and can be rolled up to fit into your carry on luggage. When not in use for ammo, they can be used to as a suitcase, or carry bag for cameras, optics, and electronic gear.

Norchill Bags come in three sizes and a variety of colors. Price starts at $39.99 for the small bag (12-can capacity) is $39.99. The 10″x12″x18″ medium bag has double the capacity (24 cans) and costs $49.99. There is also a jumbo 48-can capacity bag, 13″x13″x21″. But this is probably more capacity than you’d ever need.

To learn more about how ambient temperature (and primer choice) affect pressures (and hence velocities) you should read the article Pressure Factors: How Temperature, Powder, and Primer Affect Pressure by Denton Bramwell. In that article, the author uses a pressure trace instrument to analyze how temperature affects ammo performance. Bramwell’s tests yielded some fascinating results. For example, barrel temperature was a key factor: “Both barrel temperature and powder temperature are important variables, and they are not the same variable. If you fail to take barrel temperature into account while doing pressure testing, your test results will be very significantly affected. The effect of barrel temperature is around 204 PSI per F° for the Varget load. If you’re not controlling barrel temperature, you about as well might not bother controlling powder temperature, either. In the cases investigated, barrel temperature is a much stronger variable than powder temperature.”